1. Field of the Invention
The present invention relates, in general, to the desulfurization of flue gas or closed vessels where liquid is sprayed into a gas stream and, in particular, to a new and useful method and arrangement for measuring the pressure drop across a component contained within a flue gas desulfurization system.
2. Description of the Related Art
It is well-known that the accurate determination of liquid flow in a flue gas desulfurization (FGD) system is essential to evaluate and optimize the performance of the system. Conventional methods such as measuring pump drawn currents and pump total developed head depend largely on the condition of the pump and require a well developed knowledge of the system resistance. These methods attempt to measure the flow by following measuring the performance of the source and assuming that the rest of the system is operating as designed. Ultrasonic meters have been used for the measurements and are non-intrusive; but they require a certain length of pipe which may not be available in a lot of instances. Magnetic meters are also used but tend to be intrusive and require a straight pipe which may not be readily available.
Orifices have also been used in the pipes. However, the erosive nature of the slurry makes their use limited. Moreover, orifice meters are not suited for flow measurements in a vertical run of pipe because of the slurry deposition on the downstream face of the orifice and the continuous change in its flow characteristics. In a horizontal run of pipe, eccentric orifices are used to reduce the stream deposition upstream and downstream deposition of slurry but are still susceptible to erosion.
Some global problems encountered with orifice meters are listed below as follows. They restrict flow into the header; therefore, unless the system is designed with the orifice meter in mind, the flow characteristics of the system are expected to change with the introduction of the orifice. The flow measured by the orifice is an indication of the flow of the orifice location; and if multiple headers branch downstream of the header, there is no indication of the flow of the delivery point to the nozzle. Also, the characteristics of the orifice change as erosion takes its toll on the orifice. Furthermore, slurry from the FGD system gets into the orifice taps thereby plugging them, and rendering the orifice useless after only a few hours of operation.
Additionally, protection devices such as diaphragms have also been used. Pressure gauges with diaphragms tend to protect the gauge and overcome the plugging problem, but they have the same problems encountered with orifices.
Presently, there is no known system or method which provides for an accurate and efficient measurement of pressure drop for a component in a flue gas desulfurization vessel.